Devices containing strip advancement mechanisms for feeding strips containing medicaments are well known. Such devices can advance strips containing medicaments in blisters, or in other forms of pocket, in the strip, in a stepwise manner, past or to a mouthpiece provided on the device or inhaler so that the medicament can be inhaled through the mouthpiece. The medicament may be in a dry powder form. Such inhalers include the DISKUS® inhaler manufactured by GlaxoSmitKline, and those disclosed in U.S. Pat. No. 5,590,645, PCT Patent Application No. WO 03/061743 and US Patent Application No. US2003/0172927. The entire disclosures of each of the above publications are incorporated herein by way of reference.
Prior art inhaler devices generally feed either one or, in the case of WO 03/061743, two strips of medicament from one or two source spools within the device to or past a mouthpiece of the inhaler device. The feeding of the strip is achieved by a strip feeding mechanism that usually comprises a series of gears and/or spools within the device. The mechanism guides the strip and lead spools are provided for winding up the spent strip components.
The devices usually release the medicament from the strip at or adjacent to a mouthpiece by opening the blisters in the strip, for example by piercing, tearing or rupturing the strip, or by peeling a top layer from a bottom layer of the strip. Other forms of strip manipulation might also be used. The released medicament can then be administered by the patient by inhalation through the mouthpiece.
Generally, each blister or pocket, for example between two layers, defines or encapsulates a predetermined or pre-metered dose of medicament. Further, the top layer is usually a metal based foil cover sheet for peeling off a metal based foil base sheet having blister pockets therein. In particular, the foil will usually be a laminated metal and plastics sheet.
As previously indicated, the devices of the prior art generally rely upon one or more lead spool to wind up spent strip components. This winding action pulls unspent strip from the source spool and through the device. Some devices, however, also link the gears or spools of the strip advancement mechanism (but usually not the source spool) together so that the strip can be supported around a tortuous passage through the device. Preferably this involves rotating, driven, strip followers at each bend. They provide support for the strip for helping the strip to entrain around its path within the device.
If the strip (or one of the components) breaks or otherwise fails, e.g. by stretching, delaminating or tearing, in one of these devices, its pull-through mechanism, such as one relying upon one or more lead spool for winding up spent strip components, may no longer be able to pull the strip through the device correctly. For example, if a foil cover sheet tears, further dispensing of medicament may not be possible despite the strip continuing to be fed by the pulling of the base sheet through the device since further parts of the cover sheet might then not be peeled off the base sheet. A user, however, would not necessarily notice if the device had stopped working properly since the feed mechanism would still feel like it is functioning properly. Therefore, in the case of a failure of the peeling mechanism, there is a risk that a user might continue to use the inhaler in the false belief that it was still administering medicament, thereby under-dosing himself.
Another form of failure can occur. The cover sheet usually has a loop at its free end. That loop usually is fitted over a post on its lead spool, perhaps through a slot in the post. However, if that loop, or the post, was to fail, then further winding up of the cover sheet may not be possible. That would then prevent the cover sheet from being correctly peeled away from the base sheet. This also is undesirable.
It would therefore be desirable to provide a device that addresses, or provides an indication of, any one or more of the above potential problems.